Transition-metal catalyst component for a ziegler catalyst system, and the use of said system

ABSTRACT

A transition-metal catalyst component for a Ziegler catalyst system, obtainable by 1) mixing, in a solvent, an inorganic, oxidic carrier with 1.1) a vanadium trihalide alcohol complex of the formula VY3.nZ-OH, where Y is chlorine or bromine, n is from 1 to 6, and Z is a monovalent, saturated, aliphatic, aromatic or araliphatic hydrocarbon radical having not more than 10 carbon atoms, and 1.2) a titanium halide or a titanium trihalide/aluminum trihalide complex, where the halogen can be chlorine and/or bromine, or a titanium trihalide complex of the formula TiY3.nZ-OH or mixtures thereof, where Y is chlorine or bromine, n is from 1 to 6, and Z is a monovalent, saturated, aliphatic, aromatic or araliphatic hydrocarbon radical having not more than 10 carbon atoms, and 1.3) a compound of the formula BXnYmRp or SiXnYmRq or mixtures thereof, where X is OR, Y is chlorine, bromine or hydrogen, and R is a C1- to C18-hydrocarbon radical, with the proviso that n&gt;0 and n+m+p=3 or n+m+q=4, 2) removing the solvent by evaporation, 3) mixing the solid-phase intermediate from step 2) with 3.1) an organoaluminum catalyst component of the formula AlRmX3-m, where R is a C1- to C18-hydrocarbon radical, m is from 1 to 3, and X is OR, chlorine, bromine or hydrogen, and 3.2) an organic carboxylate or an organosilicon compound or a mixture thereof in an organic solvent, and 4) if desired, isolating the solid-phase intermediate by filtration, washing and drying, and the use thereof for the homopolymerization or copolymerization of ethene are described.

The present invention relates to a transition-metal catalyst component for a Ziegler catalyst system, obtainable by

1) mixing, in a solvent, an inorganic, oxidic carrier with

1.1) a vanadium trihalide alcohol complex of the formula VY₃ ·nZ--OH, where

Y is chlorine or bromine,

n is from 1 to 6, and

z is a monavalent, saturated, aliphatic, aromatic or araliphatic hydrocarbon radical having not more than 10 carbon atoms, and

1.2) a titanium halide or a titanium trihalide/aluminum trihalide complex, where the halogen can be chlorine and/or bromine, or a titanium trihalide complex of the formula TiY₃ ·nZ--OH or mixtures thereof, where

Y is chlorine or bromine,

n is from 1 to 6, and

z is a monavalent, saturated, aliphatic, aromatic or araliphatic hydrocabon radical having not more than 10 carbon atoms, and

1.3) a compound of the formula BX_(n) Y_(m) R_(p) or SiX_(n) Y_(m) R_(q) or mixtures thereof, where

X is OR,

Y is chlorine, bromine or hydrogen, and

R is a C₁ - to C₁₈ - hydrocarbon radical, with the proviso that n >0 and n+m +p =3 or n+m+q =4,

2) removing the solvent by evaporation,

3) mixing the solid-phase intermediate from step 2) with

3.1) an organoaluminum catalyst component of the formula AlR_(m) X_(3-m), where

R is a C₁ - to C₁₈ - hydrocarbon radical,

m is from 1 to 3, and

X is OR, chlorine, bromine or hydrogen, and

3.2) an organic carboxylate or an organosilicon compound or a mixture thereof in an organic solvent, and

4) if desired, isolating the solid-phase intermediate by filtration, washing and drying.

The present invention furthermore relates to the use of this catalyst component in a Ziegler catalyst system for preparing a homopolymer of ethene or a copolymer of ethene with minor amounts of a C₃ - to C₈ -, in particular C₄ - to C₈ -α-monoolefin by polymerizing the monomers at from 30 to 200° C., preferably from 50 to 100° C., and at from 1 to 200 bar.

Polymerization processes of this type are known and have been described, for example, in EP-A 0 166 888. The transition-metal catalyst component (1) published therein, which is obtainable from a transition-metal starting component (2b), comprising a mixture of a vanadium component and a titanium component and, if desired, a zirconium tetrahalide, allows homopolymers and copolymers of ethene to be prepared with a specific, very broad molecular weight distribution and with good productivity and grain quality of the products. However, for specific objectives, such as the preparation of high-molecular-weight, high density products, the productivity of the system and the grain quality of the resultant polymers are still inadequate.

In addition, the resistance to environmental stress cracking, the bubble stability on film blowing and the mechanical strength of the resultant films are also in need of improvement. It is also necessary to reduce the hydrocarbon-soluble components and the gel content.

EP-A 0 078 996 discloses a transition-metal catalyst component (1) which is obtainable by applying VCl₃ from an alcohol as solvent onto SiO₂ and then carrying out a second step involving reaction with an alkyl-aluminum compound. However, this catalyst component is not suitable for achieving the aim of preparing homopolymers or copolymers of ethene having good grain quality and a moderate molecular weight distribution at the same time as good productivity. In addition, the resistance to environmental stress cracking, the bubble stability on film blowing and the mechanical strength of the films obtained are still in need of improvement. It is also still necessary to reduce the amount of hydro-carbon-soluble components and the gel content.

Finally, U.S. Pat. No. 4,508,842 describes a transition-metal catalyst component (1) which is prepared by applying VCl₃ from an electron donor as a solvent onto SiO₂. However, it is again unsuitable for achieving the aim of producing polymers having good grain quality at the same time as good productivity. In addition, the resistance to environmental stress cracking, the bubble stability on film blowing and the mechanical strength of the films obtained are still in need of improvement. It is also still necessary to reduce the hydrocarbon-soluble components and the gel content.

It is an object of the present invention to provide a novel transition-metal catalyst component which, in contrast to known catalyst components, allows the preparation of a polymer, in particular a copolymer of ethene with higher α-olefins having a specific molecular weight and molecular weight distribution along with good processability, good grain quality, high resistance to environmental stress cracking, low hydrocarbon-soluble components, particularly good bubble stability on film blowing and high mechanical strength of the films and an extremely low gel content at the same time as high productivity.

We have found that this object is achieved by the transition-metal catalyst component defined at the outset, and by a process for the preparation of a homopolymer of ethene or a copolymer of ethene with minor amounts of a C₃ - to C₈ -α-monoolefin by polymerizing the monomers at from 30 to 200° C. and at from 0.1 to 200 bar by means of a Ziegler catalyst system comprising

A) a transition-metal catalyst component and

B) an organoaluminum catalyst component of the formula

AlR_(m) X_(3-m), where

R is a C₁ - to C₁₈ -hydrocarbon radical,

m is from 1 to 3, and

X is OR, chlorine, bromine or hydrogen, and

C) an additional catalyst component which is either one or more organohalogen compounds or one or more inorganic or organic nitrogen-oxygen compounds or a mixture thereof,

in which the transistion-metal catalyst component according to the invention is used as component A).

The following details apply to the individual components of the system and to individual process steps:

Examples of suitable inorganic, oxidic carriers in step 1 are silica, borosilicate and aluminosilicate, aluminum phosphate and silicon-metal cogels, where the metal may be, for example, magnesium, titanium and/or zirconium. The carriers generally have a particle diameter of from 1 to 1,000 μm, preferably from 1 to 400 μm, a pore volume of from 0.3 to 3 cm³ /g, preferably from 1 to 2.5 cm³ /g, and a surface area of from 100 to 1,000 m² /g, preferably from 200 to 400 m² /g. An aluminum silicate of the formula SiOh₂ ·aAl₂ O₃ where a is from 0 to 2, preferably from 0 to 0.5, has proven particularly successful.

The vanadium trihalide alcohol complex of step (1.1) has the formula VY₃ ·nZ--OH, where

Y is chlorine or bromine, preferably chlorine,

n is from 1 to 6, preferably from 3 to 4, and

Z is a monovalent, saturated-aliphatic or partially saturated-aliphatic, partially aromatic hydrocarbon radical having not more than 10, preferably not more than 8, carbon atoms, in particular an alkyl radical having not more than 6 carbon atoms.

The parent vanadium trihalide here can be one which is conventional in Ziegler catalyst systems. Examples of suitable alcohol components are methanol, ethanol, 2-propanol, 2-butanol and 2-methyl-2-butanol. The complexes can be prepared from vanadium trichloride and 2-propanol in tetrahydrofuran as solvents by conventional methods, eg. by the method of D.C. Bradley, M.L. Metha, Can. J. Chem., 40 (1962), 1710/3. The complexes can be employed individually or as a mixtures of a plurality of complexes.

Suitable step (1.2) components are titanium trihalides where the halogen may be chlorine and/or bromine, or titanium trihalide complexes of the formula TiY₃ ·nZ--OH, where

Y is chlorine or bromine,

n is from 1 to 6, and

Z is a monovalent, saturated, aliphatic, aromatic or araliphatic hydrocarbon radical having not more than 10 carbon atoms.

The titanium trihalide to be employed may in turn be one which is conventional in Ziegler catalyst systems, eg. the product of the reduction of a titanium tetrahalide using hydrogen, aluminum or an organoaluminum compound. For example, trichlorides of the formula TiCl₃, as produced in the reduction of titanium tetrachloride by means of hydrogen, and trichlorides of the formula TiCl₃ ·1/3AlCl₃, as produced in the reduction of titanium tetrachloride by means of metallic aluminum, have proven particularly suitable. It is also possible to employ the abovementioned titanium trihalide/alcohol complex or a titanium trihalide/aluminum trihalide/alcohol complex, to which the same applies analogously as stated above for the vanadium trihalide/alcohol complex. The titanium trihalides and titanium trichloride/alcohol complexes may be used individually or as mixtures.

Preference is given to TiCl₃, TiCl₃ ·1/3AlCl₃, TiCl₃ ·4 i-PrOH and TiCl₃ ·1/3AlCl₃ ·5 i-PrOH.

Suitable step (1.3) components are silicon or boron compounds of the formula BX_(n) Y_(m) R_(p) or SiX_(n) Y_(m) R_(q), where X is OR, Y is chlorine, bromine or hydrogen, and R is a C₁ - to C₁₈ -hydrocarbon radical, with the proviso that n >0 and n+m+p =3 or n+m+q =4. Preference is given to compounds of the formula SiX_(n) R_(q) where X is OR, and R is an aliphatic or aromatic C₁ - to C₁₈ -hydrocarbon radical, where n >0 and n+q =4. Particular preference is given to compounds of the formula SiX_(n) R_(q) where n >1, n+q =4 and R is a hydrocarbon radical having from 1 to 10 carbon atoms.

Examples of suitable compounds are trimethyl, triethyl, tripropyl, tributyl and triphenyl borate, tetramethoxy-, tetraethoxy-, tetrapropoxy-, tetrabutoxy-and tetraphenoxysilane, methyl-, ethyl-, propyl, butyl-and phenyltrimethoxysilane, -triethoxysilane, -tripro-poxysilane, -tributoxysilane and -triphenoxysilane, dimethyl-, diethyl-, dipropyl-, dibutyl- and diphenyl-dimethoxysilane, -diethoxysilane, -dipropoxysilane, -dibutoxysilane and -diphenoxysilane, trimethyl-, triethyl-, tripropyl-, tributyl- and triphenylmethoxy-silane, -ethoxysilane, -propoxysilane, -butoxysilane and -phenoxysilane, and mixed-substituted analogs thereof.

Preference is given to tri-i-propyl borate, tri-i-butyl borate, tetrapropoxy- and tetrabutoxysilane, i-propyl- and i-butyltrimethoxysilane and -triethoxysilane, di-i-propyl- and di-i-butyldimethoxysilane and -diethoxy-silane, trimethyl- and triethyl-i-propoxysilane and -i-butoxysilane.

From 0.002 to 3 mol, preferably from 0.01 to 1 mol, of the step (1.2) titanium compound and from 0.01 to 4 mol, preferably from 0.1 to 2 mol, of the step (1.3) silicon or boron compound are used per mol of the step (1.1) vanadium compound.

Suitable organic solvents in step (1) are saturated aliphatic or partially saturated-aliphatic, partially aromatic hydrocarbons containing 1 or 2 oxa oxygen atoms and from 3 to 19 carbon atoms, preferably saturated aliphatic or partially saturated-aliphatic, partially aromatic oxahydrocarbons containing one oxa oxygen atom and from 3 to 11 carbon atoms, in particular cyclized, saturated, aliphatic oxahydrocarbons containing one oxa oxygen atom and from 4 to 6 carbon atoms. Examples of suitable solvents are ethylene glycol dimethyl ether, anisole, tetrahydrofuran, dioxane and mixtures of these.

The step (3.1) component is an organoaluminum catalyst component of the formula AlR_(m) X_(3-m), where

R is a C₁ - to C₁₈ -hydrocarbon radical, preferably a C₁ - to C₁₂ -alkyl radical, in particular a C₂ - to C₈ -alkyl radical,

m is from 1 to 3, preferably from 2 to 3, in particular 2, and

X is OR, chlorine, bromine or hydrogen, preferably OR or chlorine, in particular chlorine.

Examples of suitable organoaluminum compounds are Al(C₂ H₅)₃, Al(C₂ H₅)₂ Cl, Al(C₂ H₅)₂ Br, Al(C₂ H₅)₁.5 Cl₁.5, Al(C₂ H₅)₁.5 Br₁.5, Al(C₂ H₅)Cl₂, Al(C₂ H₅)Br₂, Al(C₄ H₉)₃ , Al(C₄ H₉)₂ Cl, Al(C₄ H₉)Cl₂, Al(C₂ H₅)₂ H, Al(C₄ H₉)₂ H, Al(C₃ H₇)₂ (OC₃ H₇) or Al(C₂ H₅)₁.5 (OC₂ H₅)1.5, isoprenylaluminum and mixtures thereof. Particularly suitable aluminum compounds are those of the formula C₂ H₅ AlCl₂ or (C₂ H₅)₂ AlCl and isoprenylaluminum.

The step (1.1), (1.2) and (3.1) components are employed in mixing ratios which give an atomic ratio between the sum of the transition metals vanadium and titanium of the solid-phase intermediate in step (2) to aluminum of the organoaluminum component in step (3.1) of from 1:0.05 to 1:30, preferably from 1:0.1 to 1:5.

Suitable organic carboxylates or organic silicon compounds of step (3.2) are compounds of the following formula: ##STR1## or

R¹ R² R³ Si-E² -SiR⁴ R⁵ R⁶,

where

R¹ to R⁶ are an aliphatic, aromatic or araliphatic C₁ - to C₁₂ -hydrocarbon radical, preferably aliphatic, aromatic or araliphatic C₁ - to C₁₂ -alkyl, in particular C₂ - to C₈ -alkyl, phenyl or phenyl(C₂ -to C₈ -)alkyl,

R⁷ is hydrogen or a C₁ -C₁₂ -hydrocarbon radical, preferably hydrogen or C₁ -C₁₂ -alkyl, in particular hydrogen,

X is bromine, chlorine or an unsaturated C₂ - to C₁₈ -hydrocarbon radical, preferably bromine, chlorine or unsaturated C₂ - to C₁₂ -alkenyl, in particular chlorine or C₂ -C₈ -alkenyl,

E¹ is an element of main group V, preferably nitrogen, phosphorous or arsenic, in particular nitrogen,

E² is an element of main group VI, preferably sulfur or oxygen, in particular oxygen.

Examples of suitable organic carboxylates are methyl, ethyl, propyl, butyl, pentyl or phenyl esters of acetic acid, benzoic acid, phenylacetic acid and derivatives thereof which are substituted on the aromatic ring by alkyl. Preference is given to phenyl, benzyl, t-butyl and neopentyl esters of acetic acid, benzoic acid and phenylacetic acid.

Examples of suitable silicon compounds are trimethyl-, triethyl-, tripropyl-, tributyl-, tripentyl-, trihexyl- and triphenylchlorosilane and their analogs which are substituted by different substituents, tetra-methoxy-, tetraethoxy-, tetrapropoxy- and tetrabutoxy-silane, methyl-, ethyl-, propyl-, butyl- and phenyltri-methoxysilane, -triethoxysilane, -tripropoxysilane, -tributoxysilane and -triphenoxysilane, dimethyl-, diethyl-, dipropyl-, dibutyl and diphenyldimethoxysilane, -diethoxysilane, -dipropoxysilane, -dibutoxysilane and -diphenoxysilane, trimethyl-, triethyl-, tripropyl-, tributyl and triphenylmethoxysilane, -ethoxysilane, -propoxysilane, -butoxysilane and -phenoxysilane, hexamethyl-, hexaethyl-, hexapropyl-, hexabutyl- and hexaphenyl-disilane, hexamethyl-, hexaethyl-, hexapropyl-, hexabutyl- and hexaphenyldisilazane, and hexamethyl-, hexaethyl-, hexapropyl-, hexabutyl- and hexaphenyl-disiloxane, and mixed-substituted analogs thereof.

Preference is given to tributyl-, tripentyl-, trihexyl- and triphenylchlorosilane, tetrapropoxy- and tetrabutoxysilane, i-propyl- and i-butyltrimethoxysilane and -triethoxysilane, di-i-propyl- and di-i-butyldi-methoxysilane and -diethoxysilane, trimethyl- and triethyl-i-propoxysilane and -i-butoxysilane, hexamethyl-disilane, hexamethyldisilazane and hexamethyldisiloxane.

The solvent in step (3.2) is an organic solvent which is inert to the step (3) component. Examples of suitable solvents are hydrocarbons, such as hexane, heptane, petroleum ethers or saturated hydrocarbons which are liquid at room temperature. Preference is given to pentane, hexane and heptane.

To prepare the mixture in step (1), the vanadium and titanium components in steps (1.1), (1.2) and (1.3) are dissolved in one of the abovementioned solvents or solvent mixtures, and the inorganic, oxidic carrier is added with stirring, either as the solid or suspended in one of the abovementioned solvents or solvent mixtures, and the mixture is stirred for a further 15 to 200 minutes at room temperature. The weight ratio between the inorganic, oxidic carrier and the sum of the vanadium and titanium components in steps (1.1) and (1.2) is from 10:1 to 1:3, preferably from 5:1 to 1:2.The molar ratio between the step (1.1) vanadium component and the step (1.3) component is from 1:100 to 4.1, preferably 1:10 to 2:1.

In step (2), the solvent or solvent mixture is evaporated until the intermediate has a dry consistency. This can be carried out at elevated temperature and under reduced pressure. The dry intermediate may still contain a complexed solvent.

To prepare the mixture in step (2), a 0.1 to 50% strength by weight, preferably about 25% strength by weight, suspension of the solid-phase intermediate (2) and a 5 to 80% strength by weight, preferably about 20% strength by weight, solution of the aluminum component (3.1) are preferably prepared in separate batches in hexane, heptane, petroleum ethers or mixtures thereof. The suspension and solution are then combined with stirring in such mixing ratios that the desired weight ratio is achieved. The organic carboxylate or the organic silicon compound or a mixture thereof in step (3.2) is added to this suspension with continued stirring. However, this step (3.2) component can also be added to the solution of the aluminum component (3.1}and subsequently added to the suspension of the solid-phase intermediate (3). The suspension is stirred for from 15 to 600 minutes, preferably from 6 to 300 minutes, at from -25 to 120° C., preferably from 25 to 80° C., completing the formation of the transition-metal catalyst component, which is in the form of a suspension. This can be used directly in the form of the resultant suspension as the transition-metal catalyst component (A). If desired, the solid-phase product (3) can be isolated and then employed as the transition-metal catalyst component (A). To this end, it is separated from the liquid phase by filtration, washed with pure solvent and dried, for example under reduced pressure.

The Ziegler catalyst system for the homopolymerization or copolymerization of ethene comprises

A) the transition-metal catalyst component according to the invention,

B) an organoaluminum catalyst component of the formula AlR_(m) X_(3-m), where

R is a C₁ - to C₁₈ -hydrocarbon radical,

m is from 1 to 3, and

X is OR, chlorine, bromine or hydrogen, and

C) an additional catalyst component which is either one or more organohalogen compounds or one or more inorganic or organic nitrogen-oxygen compounds or a mixture thereof.

Suitable compounds for component (B) are those mentioned in step (3.1). Triethylaluminum and tri-i-butylaluminum have proven particularly successful. Suitable compounds for the organohalogen catalyst component (C) are saturated aliphatic halogenated hydrocarbons, olefinically unsaturated aliphatic halogenated hydrocarbons, acetylenically unsaturated aliphatic halogenated hydrocarbons, aromatic halogenated hydrocarbons and olefinically unsaturated aliphatic halogenated carboxylates, nitrogen oxides, nitroso and nitro compounds and nitrites and nitrates, such as NO, NO₂, N₂ O, nitrosodiphenylamine, nitrobenzene, nitromethane, i-butyl nitrite, i-amyl nitrite and i-propyl nitrate and mixture thereof, as mentioned, for example, in EP 166 888, U.S. Pat. No. 3,462,399 and German Laid-Open Application DE-OS 15 45 111. Preference is given to chloroform, 1,1,1-trichloroethane and trichlorofluoromethane.

Suitable polymerization processes are those of the prior art, such as suspension polymerization or dry-phase polymerization in a stirred or fluidized fixed bed, as described, for example, in U.S. Pat. No. 3,242,150, German Laid-Open Application DE-OS 32 39 883 and EP 000 4645. In these processes, the transition-metal catalyst component (A) according to the invention can be introduced into the polymerization reactor in various ways.

Thus, the transition-metal catalyst component (A), the organoaluminum component (B) and the additional catalyst component (C) can be introduced into the polymerization reactor

1. all at the same location,

2. the same 3 components at separate locations,

3. the transition-metal component (A) at one location and the mixture of (B) and (C) at a separate location, or

4. a mixture of the transition-metal component (A) and the additional catalyst component (C) at one location and the organoaluminum component (B) at a separate location.

The polymerization process, which is preferably carried out continuously, is suitable for the preparation of a homopolymer of ethene, but preferably a copolymer of ethene with minor amounts of a C₃ - to C₈ -, in particular a C₄ - to C₆ -α-monoolefin, it being possible for the latter to be in the form of individual compounds or mixtures of two or more monomers. Examples of α-monoolefins which are suitable for the copolymerization are propene, 1-n-butene, 4-methyl-1-pentene, 1-n-hexene, 1-n-heptene and 1-n-octene and mixtures thereof. In general, from 0.1 to 10 mol%, based on the copolymer, of the higher α-mono-olefin(s) are copolymerized.

The molecular weight of the polymer is adjusted using conventional regulators, in particular hydrogen.

EXAMPLES 1 TO 5 Preparation of the transition-metal catalyst component (A)

Steps (1) and (2)

16 g of silica having a particle diameter of from 20 to 45 μm, a pore volume of 1.7 cm³ /g, and a surface area of 320 m² /g, and a solution of 19 g of a vanadium trihalide/alcohol complex of the formula VCl₃ ·4 ZOH, where Z is isopropyl, 0.9 g of a titanium trihalide/aluminum trihalide/alcohol complex of the formula TiCl₃ ·1/3AlCl₃ ·4 C₃ H₇ OH and 14 g of Si(OC₄ H₉)₄ in 100 g of tetrahydrofuran were combined, and the resultant suspension was stirred briefly. The solid-phase intermediate (2) formed was subsequently isolated by evaporating the volatile con stituents in a rotary evaporator at 10 mbar and 70° C. Steps (3) and (4)

20 g of the solid-phase intermediate obtained in step (2) were suspended in 75 g of n-heptane. A solution of 7.2 g of diethylaluminum chloride (DEAC) and one of the compounds (3.2) listed in the table in the molar ratio 1:1 (DEAC:compounds) in 50 g of n-heptane was added, and the resultant suspension was stirred at 65° C. for 120 minutes and filtered, and the product was washed three times with n-heptane and dried under reduced pressure.

COMPARATIVE EXAMPLE

The transition-metal catalyst component (1) described in EP-A 0,166,888 was prepared for the comparative example.

Polymerization

A 10 liter autoclave was charged with 5 1 of i-butane, 0.1 1 of 1-butene, 6 1 (s.t.p.) of hydrogen, 0.111 g of catalyst component (A), 5 mmol of tri-i-butylaluminum as catalyst component (B) and 2 mmol of trichlorofluoromethane as the organohalogen catalyst component (C). The mixture was then polymerized for 90 minutes at 80° C. with stirring and at an ethene partial pressure kept constant at 16.5 bar by regulation. The polymerization was then terminated by decompression.

                                      TABLE                                        __________________________________________________________________________     Example           P/C.sup.1)                                                                            HLMFI.sup.2)                                                                        Density.sup.3)                                                                      x.s..sup.4)                                                                       DDI.sup.5)                               No.    Component (3.2)                                                                           g PE/g Cat.                                                                           g/10'                                                                               g/cm.sup.3                                                                          %  g                                        __________________________________________________________________________     1      Ethyl benzoate                                                                            12080  12   0.947                                                                               2.4                                                                               380                                      2      Tetraethoxysilane                                                                         12240  13   0.946                                                                               2.3                                                                               420                                      3      Trihexylchlorosilane                                                                      12790  15   0.947                                                                               3.4                                                                               380                                      4      Hexamethyldisilane                                                                        12380  14   0.946                                                                               3.1                                                                               410                                      5      Hexamethyldisiloxane                                                                      12400  12   0.946                                                                               2.5                                                                               400                                      Comparative                                                                            --         6870  16   0.947                                                                               6.4                                                                               250                                      Example                                                                        __________________________________________________________________________      .sup.1) P/C = catalyst productivity in g of PE/g of catalyst                   .sup.2) determined in accordance with DIN 53 735, 190° C. at a loa      of 21.6 kg                                                                     .sup.3) determined in accordance with DIN 53 479                               .sup.4) x.s. = xylenesoluble components                                        The xylenesoluble component of the product prepared here is the part whic      remains dissolved after a polymer solution in xylene which is clear at th      boiling point is cooled to 20° C. The concentration is adjusted to      1% strength.                                                                   .sup.5) DDI (dart drop impact) ASTM 1709, determined on films of thicknes      20 μm                                                                  

We claim:
 1. A transition-metal catalyst component for a Ziegler catalyst system, obtained bymixing, in a solvent, an inorganic, oxidic carrier with1.1) a vanadium trihalide alcohol complex of the formula VY₃ ·nZ--OH, whereY is chlorine or bromine, n is from 1 to 6, and Z is a monovalent, saturated, aliphatic, aromatic or araliphatic hydrocarbon radical having not more than 10 carbon atoms, and 1.2) a titanium halide or a titanium trihalide/aluminum trihalide complex, where the halogen can be chlorine and/or bromine, or a titanium trihalide complex of the formula TiY₃ ·nZ--OH or mixtures thereof, whereY is chlorine or bromine, n is from 1 to 6, and Z is a monovalent, saturated, aliphatic, aromatic or araliphatic hydrocarbon radical having not more than 10 carbon atoms, and 1.3) a compound of the formula BX_(n) Y_(m) R_(p) or SiX_(n) Y_(m) R_(q) or mixtures thereof, whereX is OR, Y is chlorine, bromine or hydrogen, and R is a C₁ -to C₁₈ -hydrocarbon radical, with the proviso that n >0 and n+m+p =3 or n+m+q =4, 2) removing the solvent by evaporation, 3) mixing the solid-phase intermediate from step 2) with3.1) an organoaluminum catalyst component of the formula AlR_(m) X_(3-m), whereR is a C₁ - C₁₈ -hydrocarbon radical, m is from 1 to 3, and X is OR, chlorine, bromine or hydrogen, and 3.2) an organic carboxylate or an organosilicon compound or a mixture thereof in an organic solvent, and 4) isolating the solid-phase intermediate by filtration, washing and drying.
 2. A transition-metal catalyst component as defined in claim 1, obtained using a silica- or silica/alumina-based carrier in step (1).
 3. A transition-metal catalyst component as defined in claim 1, obtained using from 0.002 to 3 mol of a titanium compound in step (1.2) and from 0.01 to 4 mol of a compound in step (1.3) per mol of a vanadium compound in step (1.1).
 4. A transition-metal catalyst component as defined in claim 1, obtained observing an atomic ratio between the sum of the transition metals vanadium and titanium in the solid-phase intermediate in step (2) and aluminum of the organoaluminum component in step (3.1) of from 1:0.5 to 1:30.
 5. A transition-metal catalyst component as defined in claim 1, obtained using an organic carboxylate of the general formula ##STR2## where R¹ and R² are a C₁ -C₁₈ -hydrocarbon radical, as component (3.2).
 6. A transition-metal catalyst component as defined in claim 1, obtained using an organosilicon compound of the general formula ##STR3## or R¹ R² R³ Si-E² SiR⁴ R⁵ Rhu 6,where R¹ to R⁶ are a C₁ - C₁₈ -hydrocarbon radical, R⁷ is hydrogen or a C₁ -C₁₂ -hydrocarbon radical, X is halogen or an unsaturated C₂ - to C₁₈ -hydrocarbon radical, E¹ is an element from main group V, and E² is an element from main group VI.
 7. A transition-metal catalyst component as defined in claim 1, obtained usingfrom 20 to 80 mol-% of the step (3.1) component and from 20 to 80 mol-% of the step (3.2) component, with the proviso that the sum is 100 mol-%. 